The application of volume texture extraction to three-dimensional seismic data – lithofacies structures exploration within the Miocene deposits of the Carpathian Foredeep

There are numerous conventional fields of natural gas in the Carpathian Foredeep, and there is also evidence to suggest that unconventional gas accumulations may occur in this region. The different seismic sig-natures of these geological forms, the small scale of amplitude variation, and the large amount of data make the process of geological interpretation extremely time-consuming. Moreover, the dispersed nature of information in a large block of seismic data increasingly requires automatic, self-learning cognitive processes. Recent developments with Machine Learning have added new capabilities to seismic interpretation, especially to multi-attribute seismic analysis. Each case requires a proper selection of attributes. In this paper, the Grey Level Co-occurrence Matrix method is presented and its two texture attributes Energy and Entropy. Haralick’s two texture parameters were applied to an advanced interpretation of the interval of Miocene deposits in order to discover the subtle geological features hidden between the seismic traces. As a result, a submarine-slope channel system was delineated leading to the discovery of unknown earlier relationships between gas boreholes and the geological environment. The Miocene deposits filling the Carpathian Foredeep, due to their lithological and facies diversity, provide excellent conditions for testing and implementing Machine Learning techniques. The presented texture attributes are the desired input components for self-learning systems for seismic facies classification

EXTRACTION OF UNDERLYING GEOLOGICAL STRUCTURE FROM SEISMIC DATA USING DATA MINING TECHNIQUES

The development of seismic-imaging technology has substantially improved the exploration of subsurface deposits of crude oil, natural gas and minerals. Recent advances in data capture, processing power and storage capabilities have enabled us to analyze large volumes of seismic data. In this study we report on the implementation of machine learning and data mining techniques for analysis of seismic data to reveal salt deposits underneath the soil. Several seismic attributes have been extracted from these datasets. Using information gain, the best six attributes (homogeneity, contrast, energy, median, peaks and average energy) have been selected for further classification. Finally we compared the results obtained using four different clustering techniques: k-means algorithm, expectation maximization algorithm, min-cut algorithm and Euclidean clustering.Computer Science, Department o

Bed properties and three-dimensional topography from radar at Rutford Ice Stream, West Antarctica

Outlet glaciers and ice streams of the Antarctic Ice Sheet provide dis-charge pathways, transporting >90% of the continents ice into the oceans. Elongated landforms beneath fast flowing ice streams form as a result of ice-bed interactions. Understanding their link to ice flow dynamics will better inform subglacial processes and allow these processes to be correctly implemented in predictive numerical flow models, thus improving predictions of future contributions to sea level rise. In this thesis, a section of the bed of Rutford Ice Stream (West Antarctica), containing numerous elongated subglacial landforms, was analysed using a suite of 2D and 3D radar data with repeat surveys. Bed properties vary spatially over a 100 m scale and imply the pat-tern of inferred basal motion in this area is more complex, and basal sliding dominated areas are more extensive, than previously assumed. Local erosion rates are high (1 m/a), indicating a mobile bed, whereas most of the bed shows no temporal change, implying stability of the basal environment. Observations of landforms shortening, and previ-ous observations of landforms extending, highlight that landforms are a non-static part of the bed. Isolated landforms appear to consist of a more rigid sediment at their upstream end with softer sediment down-stream. Some landforms contain a water body (up to 10 km length) along their crest. 3D processed data reveal a so far unseen moat (de-pression) around one landform. Dimensions of the upstream part of the moat are comparable to dimensions of the upstream end of the landform (<50 m height, <300 m width). Observations suggest land-forms are depositional features, while the moat was likely eroded. The radar and other data analysed provide detailed landform and moat ar-chitecture, at a resolution comparable to digital elevation models of deglaciated terrain, and together with interpreted properties give a solid basis for testing existing landform formation theories

Relations between seismic signals and reservoir properties of deep gas reservoirs in Northwest-Germany -Wustrow member, Rotliegend

This study tries to find the petrophysical basis for correlations between reservoir properties and seismic signals calibrated with geological information for Wustrow-sediments of the Rotliegend in NW-Germany. A secondary objective consists in explaining the large scatter of permeability for Wustrow reservoir rocks of comparable properties. The correlations were ascertained in the DGMK-project 593-8, for instance to authigenic clay mineral types and permeability. The investigations demonstrate that the differences in seismic signals (amplitude, shape and lateral coherency of seismic traces) are a product of distinct compressional field velocities (from wireline logs) and attenuation processes as in-situ bulk densities are barely varying within the investigated horizon. The regions of different clay mineral authigenesis (illite and chlorite) diverge by their average compressional in-situ speeds. The differences suffice to provoke relevant variations in seismic signals

Three dimensional quantitative textural analysis of nickel sulphide ore using X-ray computed tomography and grey level co-occurrence matrices on drill core

Alongside the global trend to mine and process lower grade and more mineralogically complex ores, there has been an increased awareness of the prevalence of ore heterogeneity. Ore texture - the interrelationship of minerals comprising a rock, has been identified as one of the primary geometallurgical indicators of ore variability. It is well known that a relationship exists between ore texture and the resultant metallurgical performance (ore hardness, throughput, liberation, grade, recovery). Consequently, there exists a need to rapidly, routinely, cost effectively, and reliably quantify ore texture and its variability prior to mining. This information can thereafter be incorporated into the geometallurgical block model and used for decision making informing mine planning, plant operation and optimisation, forecasting, and mine closure. The ability to rapidly, routinely, cost effectively and reliably quantify ore texture remains an ongoing challenge. In this study, the use of 3D X-ray computed tomography (XCT) is proposed as an innovative solution to non-destructively image the internal structure of drill core. Thereafter, an established, discipline independent two dimensional (2D) image analysis technique known as grey level co-occurrence matrices (GLCM) is specially adapted into three dimensions (3D) to quantify ore texture using XCT grey level volumes of drill core

Predicting Oligocene reservoir potential in the deep-water Western Niger Delta : an integrated basic modelling and diagenetic study

This study presents a multidisciplinary integrated approach undertaken in predicting the reservoir potential of an untapped deeper Oligocene succession located offshore of the western Niger Delta. The shallower Miocene sands are known to have excellent reservoir quality with porosities exceeding 30 % and permeability in the Darcy range. The study revealed a distinctive geometry in the deep marine depositional systems around mud diapirs. Unlike shallower Miocene reservoirs that are characterised by highly amalgamated channel systems, the Oligocene systems’ depositional pattern shows a transition from a confined channel to a weakly confined lobate morphology, particularly when the channel system approaches depressions flanked by mud diapirs. High seismic reflection amplitudes suggest they are sand-rich and possibly hydrocarbon bearing. SEM Photomicrographs reveal a rare presence of quartz overgrowth in the Middle Miocene interval that increases in volume to less than 3% in the Lower Miocene reservoirs, suggesting that the deeper Oligocene reservoirs that are buried under higher temperature conditions are likely to have significant quartz cement. Wireline log evaluation from the single well that penetrated part of the Oligocene succession supports this claim, with estimated reservoir properties, particularly porosity and permeability, being significantly lower in the Oligocene sands compared to the shallower Miocene reservoirs. Of the 7 units of Oligocene sands encountered in this well, 3 sand units are noted to be thin bedded, highly compacted with low porosity. Results from basin modelling reveal that the Oligocene reservoirs have been subjected to maximum temperatures greater than 70˚ C from Early Miocene to present day and have had around 13 % of the pore space occluded by quartz cement. The results of this integrated approach suggest that the potential Oligocene reservoir within the vicinity of the study area is likely to have its reservoir quality partially compromised by quartz cementation. However, by considering the time of charge versus the time of significant quartz cementation, it is likely that no more than 7% of the Oligocene pore space is cemented. In all 4 modelled hydrocarbon accumulations, peak hydrocarbon saturation was attained between 15 and 8Ma, predating the onset of significant quartz cementation below 7Ma

Research Article 3-D Seismic Attribute Analysis for Enhanced Prospect Definition of "Opu Field'', Coastal Swamp Depobelt Niger Delta, Nigeria

Background and Objective: Analysis of seismic attributes has been an integral part of reflection seismic interpretation for over two decades now. Seismic attributes facilitates structural and stratigraphic interpretation as well as offer hints to formation type and fluid content estimation with the potential benefit of detailed reservoir characterization. The current study evaluated the use of seismic attributes generated from 3D seismic and well log data for characterization of the reservoirs of ʻʼOpu Fieldʼʼ, Coastal Swamp Depobelt, Niger Delta. Materials and Methods: Root mean square (RMS) amplitude, instantaneous frequency and interval average maps were extracted on seismic events with pronounced bright and dim spots. These maps were used to establish the diagnostic ability of 3D seismic attribute analysis in enhancing seismic interpretation and volumetric estimation of the mid Miocene to Pliocene Agbada Formation reservoirs within the Coastal Swamp Depobelt, Niger Delta basin. The methodology involved a well-defined procedure which included the delineation of the various lithologies from the gamma ray log, identification of reservoirs from the resistivity log, regional well correlation, determination of petrophysical parameters, horizon and fault mapping, time to depth conversion, attribute analysis and reserve estimation. Results: Two main reservoirs identified as Sand-A and Sand-B were mapped in the study area using seismic data. Similarly, seven faults labelled F1-F7 and four horizons were mapped within the field. Depth structure maps generated revealed a massive Northeast-Southwest (NE-SW) trending anticlinal structure. Petrophysical analysis revealed a mean porosity value of 18% while the mean permeability values ranged from 63-540 md across the two reservoirs. Water saturation and volume of shale (Vsh) across the reservoirs ranged from 38-90 and 17-82%, respectively. Conclusion: This study revealed that the“Opu Field” has high hydrocarbon potentials and excellent petrophysical characteristics favourable for hydrocarbon accumulation and production. The benefits of integrating structural interpretation, petrophysical evaluation and seismic attributes analysis in prospect identification and reservoir prediction was therefore highlighted in this study

Hardrock Seismic Reflection Through Cover: Defining Controls on Mineralization via Reflection Attribute Analysis

This study attempts to modify oil and gas industry seismic processing and interpretation techniques for use in Carlin-type deposit (CTD) gold exploration. Magmatic and deformation overprints on the Nevada carbonate platform-slope setting present challenges in seismic interpretation when compared to conventional seismic data, which is more commonly imaged in petroliferous basins with low levels of deformation. Barrick Gold Corporation provided 2D seismic reflection data for this case study, which assesses the viability of certain seismic practices when applied to hardrock seismic data collected in NE Nevada. Initial seismic interpretations of the pre-stack depth migrated (PSDM) sections located first-order structures and enhanced the geological model. This study uses derivatives of the PSDM, called seismic attributes, in an attempt to improve interpretability. Seismic attributes can reveal structural and stratigraphic features that are not apparent in the conventional PSDM amplitude data. Attribute analysis in this study leverages correlations made from a seismic response database of ~500 petrophysical drill core samples. These petrophysical measurements indicate that the ore zone exhibits a porosity, acoustic impedance, decarbonatization relationship that is distinguishable from unaltered rock. Down-hole geophysical data suggest an even larger contrast between altered and unaltered limestone. Given sufficient data quality, these observations make attribute analysis for detection of CTD alteration viable. An exhaustive calculation of attributes applied to one 2D reflection profile, which transects the Goldrush CTD resource, suggests that energy- and frequency-based attributes best highlight the ore zone, which is expressed as a chaotic zone of reduced amplitude within one 2D profile. RMS amplitude and instantaneous amplitude identify broad zones of low amplitude whereas an average frequency attribute highlights possible high-frequency attenuation effects in the vicinity of the ore-zone. The sweetness and frequency washout attributes combine frequency and amplitude attributes to more effectively highlight the ore zone. However, the erratic response of sweetness and frequency washout suggest that they may be negatively affected by noise. One structural model is also presented, which used the instantaneous phase attribute to better visualize possible thrust faulting